1. Field of the Invention
The present invention relates to a door frame for motor vehicles which includes a window channel laterally defined by an outer door panel and an inner door panel, wherein the outer door panel and the inner door panel are provided adjacent to the window opening with longitudinally extending stiffening or reinforcement members located in the window channel.
2. Description of the Related Art
The configuration of the window channel of a door frame for a motor vehicle is of particular importance when the effects of front or rear collisions are to be taken into consideration as the most frequent accidents. Moreover, when constructing the window channel, it is also important to take into consideration the stresses occurring during a side impact.
For example, the longitudinal forces resulting from a frontal crash are conducted through longitudinal girders/beams and through the upper longitudinal girder, the A-column and the window channel into the rear portion of the vehicle. The window channel forms the most important structural component in this respect because it must stabilize the passenger cell. The window channel is particularly stressed with respect to buckling and bending. Buckling of the window channel must never occur.
The window channel is formed towards the outside by an outer door panel and towards the passenger cell by an inner door panel. In the past, a plurality of stiffening or reinforcement members have been integrated into the window channel for achieving a stable construction of the window channel. These reinforcement members are composed of deformed sheet metal pieces which are mounted in the longitudinal direction of the vehicle adjacent the window opening located above the window channel and on the oppositely located surfaces of the outer door panel and the inner door panel. The reinforcement members are usually attached by spot welding. Moreover, additional reinforcement sheet metal pieces (corner plates) are provided in the areas of the frame walls forming the front and end of the window channel.
First of all, this known construction has the disadvantage that a large number of reinforcement members are used. Also, because of their open configuration, the stiffness with respect to buckling and bending of the reinforcement members is limited. Moreover, there is the danger that the elastic joints between the individual reinforcement members may open when loads occur.